JP2019209739A - Steering system - Google Patents

Abstract

To suppress, in a steering system that includes an electric steering device and a fluid-pressure steering device, reduction in moving force acting on a steering shaft and due to an abnormality in the fluid-pressure steering device.SOLUTION: According to this steering system, torque applied to a torsion bar by an electric steering device is applied to a steering shaft as moving force via a steering gearbox and the moving force by the fluid pressure of the fluid-pressure steering device is applied to the steering shaft. When, however, there is an abnormality in the fluid-pressure steering device, the moving force by the fluid pressure decreases. Hence, according to this steering system, the torque applied to the torsion bar by an electric motor is increased when there is the abnormality in the fluid-pressure steering device more than a case in which the fluid-pressure steering device is normal. Consequently, reduction of the moving force acting on the steering shaft due to the abnormality of the fluid-pressure steering device can be well suppressed.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a steering system that is mounted on a vehicle and steers wheels.

  Patent Literature 1 describes a steering assist system including an electric assist device including an electric motor and a hydraulic assist device that is operated by hydraulic pressure. In this steering assist system, the output of the electric assist device and the output of the hydraulic assist device are added together and output.

Special table 2007-522019

  The subject of this invention is suppressing the fall of the moving force which acts on the steering shaft resulting from the abnormality of a hydraulic steering apparatus in the steering system provided with the electric steering apparatus and the hydraulic steering apparatus. is there.

Means, actions and effects for solving the problem

  The turning system of the present invention includes an electric turning device provided with an electric motor and a hydraulic pressure turning device operated by hydraulic pressure. In this turning system, the torsion bar is engaged with the turning shaft via the steering gear box, the torque is applied to the torsion bar by the electric motor, and the torsion bar is applied by the hydraulic turning device. A hydraulic pressure corresponding to the torque is applied to the steered shaft. As described above, the torque applied to the torsion bar by the electric steering device is applied to the steered shaft as a moving force through the steering gear box, and the moving force by the hydraulic pressure of the hydraulic steering device is applied. However, when the hydraulic steering device is abnormal, the moving force due to the hydraulic pressure becomes small. Thus, in the present steering system, the torque applied to the torsion bar by the electric motor is increased when the hydraulic steering device is abnormal than when it is normal. As a result, it is possible to satisfactorily suppress a reduction in moving force acting on the steered shaft due to an abnormality in the hydraulic steered device.

It is a figure which shows typically the steering system which is an Example of this invention. It is sectional drawing of the gear box of the hydraulic assistance mechanism of the said steering system. It is sectional drawing of the control valve of the said gearbox. It is a figure which shows the valve characteristic of the said control valve memorize | stored in the memory | storage part of steering ECU of the said steering system. It is a figure which shows the relationship between the target lateral acceleration memorize | stored in the said memory | storage part, and the output torque of an electric motor. It is a figure which shows the relationship between the steering torque memorize | stored in the said memory | storage part, and the output torque of an electric motor. It is a flowchart showing the electric motor control program memorize | stored in the said memory | storage part. It is a flowchart showing a part of said electric motor control program. It is a figure which shows notionally the LTA control performed in the said steering system. It is a figure which shows the moving force in case the hydraulic assistance mechanism is abnormal in the conventional steering system.

  Hereinafter, a steering assist system as a turning system mounted on a vehicle according to the present embodiment will be described in detail based on the drawings.

  As shown in FIG. 1, the steering assist system according to the present embodiment assists the operation of a steering wheel 10 as a steering member by a driver to steer left and right front wheels 12, 14 that are steering wheels of a vehicle. There is a function as an automatic steering system that can steer the left and right front wheels 12 and 14 even if the driver does not operate the steering wheel 10.

The left and right front wheels 12, 14 are connected by knuckle arms 16, 17, tie rods 18, 19, and a rack bar 20 as a turning shaft. Further, the steering wheel 10 is connected to the rack bar 20 via a steering gear box (hereinafter simply referred to as a gear box) 22.
The gear box 22 includes a rack and pinion mechanism as shown in FIG. The steering wheel 10 is connected to a pinion gear 28 via a steering shaft, a torsion bar 23 and the like, and the pinion gear 28 is meshed with a tooth portion of the rack bar 20. Thereby, rotation of the steering wheel 10 is converted into movement of the rack bar 20 in the vehicle width direction (left-right direction), and the left and right front wheels 12, 14 are steered. Note that the torsion bar 23 is integrally connected to the pinion gear 28 at one end and rotatably connected to the steering wheel 10 (steering shaft) at the other end.

  The steering assist system includes a hydraulic pressure assist mechanism 24 and an electric assist mechanism 26. The hydraulic assist mechanism 24 includes a power cylinder 30 provided on the rack bar 20, a control valve 34 provided on the gear box 22, and the like. The electric assist mechanism 26 includes an electric motor 38 that applies torque to the torsion bar 23.

  The power cylinder 30 includes a housing 42, a piston 44 formed on the rack bar 20, and a right chamber 46 and a left chamber 48 partitioned by the piston 44. A hydraulic pump 52 and a reservoir 54 that are operated by the engine 40 are connected to the right chamber 46 and the left chamber 48 via the gear box 22. Note that the flow rate of the hydraulic fluid supplied from the hydraulic pump 52 to the gear box 22 is substantially constant by a flow rate control mechanism (not shown).

  As shown in FIG. 3, the control valve 34 includes a rotary valve 60 and a control valve shaft 62. The control valve shaft 62 is connected to the torsion bar 23 so as to be integrally rotatable at one end, and a hydraulic pressure is applied to the other end by a reaction force applying device (not shown). A plurality of fluid passages connected to the hydraulic pump 52, the reservoir 54, the right chamber 46, and the left chamber 48 are formed in the rotary valve 60 so as to extend in the radial direction. A groove or the like is formed. By changing the relative phase of the control valve shaft 62 with respect to the rotary valve 60, the flow area between each of the hydraulic pump 52 and the reservoir 54 and each of the right chamber 46 and the left chamber 48 is controlled.

  In FIG. 3, for example, the flow area between the hydraulic pump 52 and the right chamber 46 is increased by the rotation of the control valve shaft 62 in the right direction, and the flow path between the hydraulic pump 52 and the left chamber 48 is increased. The area is reduced. Further, the flow path area between the reservoir 54 and the left chamber 48 is increased, and the flow path area between the reservoir 54 and the right chamber 46 is decreased. The hydraulic fluid of the hydraulic pump 52 is supplied to the right chamber 46, and the hydraulic fluid in the left chamber 48 is allowed to flow out to the reservoir 54. The rack bar 20 is moved in the direction indicated by the arrow α (see FIG. 1), and the left and right front wheels 12, 14 are steered to the right. By rotating the control valve shaft 62 in the left direction, the flow path area between the hydraulic pump 52 and the left chamber 48 is increased, and the flow path area between the right chamber 46 is decreased. Further, the flow path area between the reservoir 54 and the right chamber 46 is increased, and the flow path area between the left chamber 48 and the left chamber 48 is decreased. The hydraulic fluid of the hydraulic pump 52 is supplied to the left chamber 48, and the hydraulic fluid in the right chamber 46 is allowed to flow out to the reservoir 54. The rack bar 20 is moved in the direction opposite to the arrow α, and the left and right front wheels 12 and 14 are steered leftward.

  In the control valve 34, the relative phase of the control valve shaft 62 with respect to the rotary valve 60 is changed in accordance with the twist of the torsion bar 23. Therefore, in the control valve 34, as shown in FIG. 4, when the absolute value of the torque T is large between the torque T applied to the torsion bar 23 and the hydraulic pressure controlled by the control valve 34, it is smaller than The relationship where the hydraulic pressure increases is established. Further, the valve characteristics that are the relationship between them are determined by the shape of the control valve shaft 62 and the rotary valve 60, and the like.

In the electric assist mechanism 26, the electric motor 38 applies an assisting torque, which is a torque for assisting the driver to operate the steering wheel 10, to the torsion bar 23, but the driver does not operate the steering wheel 10. Even in this case, torque may be applied to the torsion bar 23.
As shown in FIG. 1, in the present embodiment, the electric assist mechanism 26 is provided on the steering wheel side (which can be referred to as the upstream side) of the gear box 22 of the torsion bar 23. The mechanism 26 and the hydraulic pressure assist mechanism 24 are provided in series. Therefore, a torque is applied to the torsion bar 23 by the electric motor 38, and a moving force due to a hydraulic pressure corresponding to the torque applied to the torsion bar 23 by the electric motor 38 is applied to the rack bar 20 by the hydraulic pressure assist mechanism 24. Further, the torque applied to the torsion bar 23 by the electric motor 38 is directly applied as a moving force to the rack bar 20 via the gear box 22. As described above, a moving force is applied to the rack bar 20 by at least the electric assist mechanism 26 and the hydraulic assist mechanism 24, and the left and right front wheels 12, 14 are steered.

  The steering assist system includes a steering ECU 100 mainly composed of a computer. The steering ECU 100 includes an execution unit 100c, a storage unit 100m, an input / output unit 100i, and the like. The input / output unit 100i includes a torque sensor 110 that detects torque applied to the torsion bar 23, and a hydraulic assist mechanism 24. A hydraulic pressure sensor 112 that detects the hydraulic pressure P, an imaging device 114 provided in the vehicle, and the like are connected, and an electric motor 38 and the like are connected.

The torque sensor 110 detects the torque applied to the torsion bar 23 by at least one of the rotation operation of the steering wheel 10 and the operation of the electric motor 38.
As described above, the hydraulic pressure sensor 112 detects the control hydraulic pressure of the control valve 34 of the hydraulic pressure assist mechanism 24, and the control hydraulic pressure of the control valve 34 is controlled by the right chamber 46 or the left chamber of the power cylinder 30. 48, the fluid pressure in the right chamber 46 or the left chamber 48 can be detected.

  The imaging device 114 can include, for example, a camera 118 that captures the front and front sides of the vehicle, and a camera ECU 120 that processes an image captured by the camera 118. The camera ECU 120 is mainly a computer, and as shown in FIG. 9, based on the image captured by the camera 118, this vehicle (a vehicle equipped with the imaging device 114, hereinafter referred to as the own vehicle). By specifying the lane markings XR and XL located on both sides of the V, the lane Y, which is the lane in which the host vehicle V is traveling, is specified, and the relative positional relationship between the predetermined target travel line Z and the host vehicle V ( For example, the center distance Dc, which is the distance between the center line CV of the host vehicle V and the target travel line Z, can be acquired. The target travel line Z can be a line that passes through the center of the lane Y, for example.

  In the steering assist system configured as described above, LTA (Lane Tracing Assist) control is performed. The LTA control is steering control performed in this embodiment so that the host vehicle V travels along the target travel line Z. In the LTA control, for example, the left and right front wheels 12 and 14 are automatically steered by the control of the electric motor 38 so that the center distance Dc acquired by the camera ECU 120 becomes small. When the LTA control is performed, the driver usually does not rotate the steering wheel 10. Therefore, it can be considered that the torque from the electric motor 38 is applied to the torsion bar 23 without applying the steering torque of the steering wheel 10 by the driver.

  For example, a target operation angle, which is an operation angle of the steering wheel 10 necessary for reducing the center distance Dc, is acquired based on the center distance Dc, and the target turning angles of the left and right front wheels 12, 14 are acquired based on the target operation angle. Is acquired, the target yaw rate of the vehicle is acquired based on the target turning angle, and the target lateral acceleration is acquired based on the target yaw rate. Then, torque is applied to the torsion bar 23 by the electric motor 38 so that the actual lateral acceleration approaches the target lateral acceleration. In other words, the torque of the torsion bar 23 necessary for realizing the target lateral acceleration is output by the electric motor 38.

  However, when the hydraulic pressure assist mechanism 24 cannot generate the hydraulic pressure corresponding to the torque applied to the torsion bar 23 due to an abnormality in the hydraulic pressure assist mechanism 24, the target lateral acceleration is not realized, and the LTA It becomes difficult to control well. For example, as shown in FIG. 10, when the target lateral acceleration is the same and the hydraulic pressure assist mechanism 24 is normal, a large moving force is applied as shown by the broken line, but the hydraulic pressure assist mechanism 24 Is abnormal, as shown by the solid line, the hydraulic pressure acting on the power cylinder 30 is reduced, so that the moving force due to the hydraulic pressure is reduced, thereby reducing the moving force acting on the rack bar 20. It is. The abnormality of the hydraulic pressure assist mechanism 24 means that the torsion bar is caused by the case where the hydraulic pressure cannot be generated due to the disconnection of the pipe, the failure of the pump 52 or the like, or due to the liquid leak at the connection portion of the pipe or the pipe. The case where the hydraulic pressure according to the torque applied to 23 cannot be generated corresponds to this case.

  The abnormality of the hydraulic pressure assist mechanism 24 is detected based on the hydraulic pressure of the hydraulic pressure assist mechanism 24 or the like. For example, when the actual fluid pressure P detected by the fluid pressure sensor 112 is lower than the abnormality determination threshold value Pth determined by the torque applied to the torsion bar 23, it is detected that the fluid pressure assist mechanism 24 is abnormal. Can be. Based on the torque Ts applied to the torsion bar 23 detected by the torque sensor 110 and the valve characteristics shown in FIG. 4, the hydraulic pressure Pa obtained when the hydraulic pressure assist mechanism 24 is normal is acquired. The lower limit value of the appropriate range determined by the hydraulic pressure Pa can be set as the abnormality determination threshold value Pth. In this case, both an abnormality in which the hydraulic pressure cannot be generated due to piping disconnection or the like and an abnormality in which the hydraulic pressure corresponding to the torque cannot be generated due to liquid leakage or the like are detected. .

  Note that the abnormality determination threshold value Pth may be a small value near zero. Then, when the actual fluid pressure P detected by the fluid pressure sensor 112 is lower than the abnormality determination threshold value Pth that is a value near 0, the fluid pressure assist mechanism 24 is detected to be abnormal. be able to. In this case, an abnormality in which the hydraulic pressure cannot be generated due to a missing pipe or the like is detected.

In the present embodiment, when the hydraulic assist mechanism 24 is abnormal, the torque output by the electric motor 38 is made larger than when it is normal.
A torque determination map that represents the relationship between the target lateral acceleration and the target torque that is the output torque of the electric motor 38 is stored in advance, and the electric motor 38 uses the torque determination map and the target lateral acceleration determined in the LTA control based on the torque determination map. The target torque to be output is determined. As the torque determination map, a normal time map when the hydraulic pressure assist mechanism 24 is normal, which is represented by a broken line in FIG. 5, and a hydraulic pressure assist mechanism 24, which is represented by a solid line. An abnormal time map in the case where is abnormal is stored in the storage unit 100m in advance. The abnormal time map is set so that the target torque of the electric motor 38 when the target lateral acceleration Gy * is the same as the normal time map is larger (Tg1> Tg2).
In the LTA control, when the hydraulic pressure assist mechanism 24 is normal, the target torque of the electric motor 38 is determined according to the normal time map, and when the hydraulic pressure assist mechanism 24 is abnormal, according to the abnormal time map. It is determined.

On the other hand, when the LTA control is not performed, for example, when the present steering system functions as a power steering system, an assist torque that is a magnitude corresponding to the steering torque applied by the driver is electrically driven. It is output by the motor 38. However, when the hydraulic assist mechanism 24 is abnormal, the front wheel steering angle intended by the driver cannot be obtained.
Therefore, when the hydraulic assist mechanism 24 is abnormal, even if the steering torque applied by the driver is the same as in the normal case, the target torque that is the target value of the assisting torque applied by the electric motor 38 is Increased.

  In this embodiment, as the torque determination map, the normal time map when the hydraulic pressure assist mechanism 24 is normal, which is indicated by a broken line in FIG. 6, and the hydraulic pressure assist mechanism 24, which is indicated by a solid line in FIG. 6, are abnormal. The abnormal time map is stored in the storage unit 100m in advance. The abnormal time map is set so that the target torque of the electric motor 38 when the steering torque Ts * is the same as that of the normal time map is larger (Ts1> Ts2).

The electric motor control program in the present embodiment is represented by the flowchart of FIG. The electric motor control program is executed at predetermined time intervals.
In step 1 (hereinafter abbreviated as S1), it is determined whether or not the electric assist mechanism 26 is normal. For example, when the electric motor 38 is disconnected, it is detected as abnormal. When the electric assist mechanism 26 is abnormal, S2 and the subsequent steps are not executed. However, when the electric assist mechanism 26 is normal, the steps after S2 are executed.

  In S2, a torque determination map is selected. As shown in the flowchart of FIG. 8, the torque determination map is selected by detecting the hydraulic pressure P of the hydraulic pressure assist mechanism 24 by the hydraulic pressure sensor 45 and the torque applied to the torsion bar 23 by the torque sensor 110 in S21. T is detected. Then, an abnormality determination threshold value Pth is determined based on the detected torque T and the valve characteristic of FIG. 4, and in S22, it is determined whether or not the detected hydraulic pressure P is lower than the abnormality determination threshold value Pth. Is done. If the determination in S22 is NO and it is not detected that the hydraulic pressure assist mechanism 24 is abnormal (normal), the normal time map is selected in S23, the determination in S22 is YES, and the hydraulic pressure If it is detected that the assist mechanism 24 is abnormal, an abnormal map is selected in S24.

  In S3, it is determined whether LTA control is permitted. The LTA control is permitted when the steering torque Ts applied to the torsion bar 23 by the driver's operation of the steering wheel 10 is smaller than a set value, or when the direction indicating switch (not shown) is OFF. In other words, when the steering wheel 10 is operated by the driver with a steering torque equal to or greater than the set value, or when the direction indicator switch is ON, the driver intends to drive the vehicle away from the target travel line Z. Since it is estimated that there is, LTA control is prohibited.

  When the driver is operating the steering wheel 10, the detected value of the torque sensor 110 is the assist torque applied by the electric motor 38 and the steering torque Ts applied by the driver's operation of the steering wheel 10. And the sum. On the other hand, the ratio between the assist torque applied by the electric motor 38 and the steering torque applied by the driver is predetermined. Therefore, the steering torque Ts applied by the driver based on the detection value of the torque sensor 110 can be acquired.

  If the determination in S3 is YES, in S4, the center distance Dc is acquired based on information from the camera ECU 120, and in S5, the target lateral acceleration Gy * is acquired based on the center distance Dc. In S6, the target torque is determined based on the torque determination map selected in S2 and the acquired target lateral acceleration Gy *. In S7, the electric motor 38 is controlled so that the target torque is output. The

  On the other hand, if the determination in S3 is NO, the steering torque Ts * is acquired based on the detection value of the torque sensor 110 in S8. In S9, the target torque is determined based on the torque determination map selected in S2 and the acquired steering torque Ts *, and in S7, the electric motor 38 is controlled so that the target torque is output. .

  As described above, in this embodiment, when the hydraulic pressure assist mechanism 24 is abnormal, the abnormal time map is selected, and the electric motor 38 is controlled based on the abnormal time map. Therefore, when the hydraulic pressure assist mechanism 24 is abnormal, a larger torque is output by the electric motor 38 than when it is normal. As a result, it is possible to satisfactorily suppress a decrease in the moving force acting on the rack bar 20 due to the abnormality of the hydraulic pressure assist mechanism 24. The LTA control can be performed satisfactorily, and the left and right front wheels 12, 14 can be steered according to the driver's intention.

  As described above, in the present embodiment, the electric assist mechanism 26 corresponds to the electric steering device, and the hydraulic assist mechanism 24 corresponds to the hydraulic steering device. Torque sensor 110, hydraulic pressure sensor 112, part of steering ECU 100 that stores the electric motor control program represented by the flowchart of FIG. 7, a part that executes it, a part that stores a normal time map and an abnormal time map of storage unit 100m, etc. Thus, an electric motor control device is configured. Among them, the torque sensor 110, the hydraulic pressure sensor 112, the part that stores S21 and 22 of the steering ECU 100, the part that executes the abnormality detection unit and the abnormality detection device are configured, the part that stores S24 and S7, and the part that executes The abnormal-time motor control unit is configured by a portion of the storage unit 100m that stores the abnormal-time map.

  In the above embodiment, the aspect of the LTA control is merely an example. For example, as the LTA control, the left and right front wheels 12 and 14 are steered so that the host vehicle V does not deviate from the lane Y. it can. If a normal time map is set in the default state, a switching command from the normal time map to the abnormal time map can be issued in S23. This mode also corresponds to selection of either the normal time map or the abnormal time map. Furthermore, the structure of the gear box 22 is not limited to that in the above-described embodiment, and the present invention can be implemented in various forms that are modified and improved based on the knowledge of those skilled in the art.

  20: Rack bar 22; Gear box 23: Torsion bar 24: Fluid pressure assist device 26: Electric assist device 28: Pinion 30: Power cylinder 32: Gear box 34: Rotary valve 38: Electric motor 100: Steering ECU 110: Torque sensor 112: Fluid pressure sensor 114: Imaging device

Patentable invention

Hereinafter, the claimable invention will be described.
(1) The left wheel and the right wheel of the vehicle are connected to each other, and the torsion bar moves the steered shaft engaged through the steering gear box, thereby turning the left wheel and the right wheel. A steering system,
An electric turning device comprising an electric motor for rotating a portion of the torsion bar upstream of the steering gear box;
A hydraulic steering device that applies a moving force by hydraulic pressure according to the torque applied to the torsion bar to the steering shaft;
An electric motor control device for controlling the electric motor, the electric motor control device,
When the hydraulic pressure of the hydraulic steering device is lower than the torque applied to the torsion bar, an abnormality detection unit that detects that the hydraulic steering device is abnormal,
An abnormality that controls the electric motor so that the output torque of the electric motor is greater when the abnormality detection unit detects that the hydraulic steering device is abnormal than when it is not detected as abnormal. A steering system including an hour motor control unit.

(2) An abnormality determination in which the abnormality detecting unit determines the hydraulic pressure of the hydraulic steering device based on a predetermined relationship between the hydraulic pressure of the hydraulic steering device and the torque applied to the torsion bar. The steering system according to item (1), wherein when the pressure is lower than the threshold value, it is detected that the hydraulic steering device is abnormal.
In the abnormality of the hydraulic steering device detected in this section, in the hydraulic steering device, the abnormality that cannot generate the hydraulic pressure of the appropriate height according to the torque, and in the hydraulic steering device, An abnormality that cannot generate hydraulic pressure is included.

(3) A lateral acceleration dependency control unit that controls the output torque of the electric motor so that the lateral acceleration acting on the vehicle approaches a target lateral acceleration determined based on a traveling state of the vehicle. Including
When the lateral acceleration dependence control unit is a normal time map that is a relationship between the target lateral acceleration and the output torque when the hydraulic steering device is normal, and when the hydraulic steering device is abnormal A storage unit that stores an abnormal time map that is a relationship between the target lateral acceleration and the output torque, and the normal time map and the abnormal time map that are stored in the storage unit based on a detection result by the abnormality detection unit A steering system according to item (1) or (2), including a map selection unit that selects any of the above.
A lateral acceleration dependence control unit (a portion that performs LTA control) includes a portion that stores S4 to 7, 23, and 24 of the steering ECU 100, a portion that executes S4, a portion that executes, a portion that stores a normal time map and an abnormal time map, The map selection part is comprised by the part which memorize | stores S23 and 24 of steering ECU100, the part to perform, etc. of them.

(4) A steering wheel as a steering member steerable by a driver is connected to the torsion bar,
A power steering control unit that controls the electric motor so that the electric motor control device outputs an assisting torque that is a torque corresponding to a steering torque that is a torque applied to the torsion bar by an operation of the steering wheel; Output
The power steering control unit has a normal time map that is a relationship between the steering torque and the output torque when the hydraulic steering device is normal, and the steering when the hydraulic steering device is abnormal. A storage unit for storing an abnormal time map that is a relationship between torque and the output torque, and a map selection unit that selects either the normal time map or the abnormal time map based on a detection result by the abnormality detection device The steering system according to (1) or (2).
The power steering control unit is configured by a part that stores S7 to 9, 23, and 24 of the steering ECU 100, a part that executes it, a part that stores the normal time map and the abnormal time map of the storage unit 100m, and the like.

(5) The gear box includes a rack and pinion mechanism,
The torsion bar is connected to the pinion gear so as to be integrally rotatable, and in the gear box, the pinion gear is engaged with a tooth portion of a rack bar that is the turning shaft. A steering system according to any one of the above.
For example, the torsion bar is integrally connected to a pinion gear at one end and rotatably connected to a steering wheel (steering shaft) that can be operated by a driver at the other end. It may be engaged with the electric motor at a portion upstream from the connecting portion. In the torsion bar, the engagement portion with the electric motor is considered to be located on the downstream side (gear box side) from the connection portion with the steering shaft.

(6) The left wheel and the right wheel are connected by connecting the left wheel and the right wheel of the vehicle, and the torsion bar moves the steered shaft engaged through the steering gear box, thereby turning the left wheel and the right wheel. A steering system,
An electric turning device comprising an electric motor for rotating a portion of the torsion bar upstream of the steering gear box;
A hydraulic steering device that applies a moving force by hydraulic pressure according to the torque applied to the torsion bar to the steering shaft;
A steering system including an abnormality detection device that detects that the hydraulic pressure steering device is abnormal when a hydraulic pressure of the hydraulic pressure steering device is lower than a predetermined abnormality determination threshold value.
The technical features described in any one of the items (1) to (5) can be employed in the steering system described in this item.
The abnormality determination threshold value can be a value near 0, for example.

Claims (1)

A steering system that connects the left wheel and the right wheel of the vehicle, and steers the left wheel and the right wheel by moving a turning shaft with a torsion bar engaged through a steering gear box. Because
An electric turning device comprising an electric motor for rotating a portion of the torsion bar upstream of the steering gear box;
A hydraulic steering device that applies a moving force by hydraulic pressure according to the torque applied to the torsion bar to the steering shaft;
An electric motor control device for controlling the electric motor, the electric motor control device,
When the hydraulic pressure of the hydraulic steering device is lower than the torque applied to the torsion bar, an abnormality detection unit that detects that the hydraulic steering device is abnormal,
An abnormality that controls the electric motor so that the output torque of the electric motor is greater when the abnormality detection unit detects that the hydraulic steering device is abnormal than when it is not detected as abnormal. A steering system including an hour motor control unit.

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